radioactive decay


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Related to radioactive decay: alpha decay, half life, radioactivity

radioactive decay

(ray-dee-oh-ak -tiv) The spontaneous transformation of one atomic nucleus into another with the emission of energy. The energy is released in the form of an energetic particle, usually an alpha particle, beta particle (i.e. an electron), or positron, sometimes accompanied by a gamma-ray photon. The unstable isotopes of an element that can undergo such transformations are called radioactive isotopes, or radioisotopes. The emission of a particle from the nucleus of a radioisotope results in the production of an isotope of a different element, as in the beta decay of carbon–14 to nitrogen–14 or the alpha decay of radium–226 to radon–222. The isotope produced is itself often radioactive.

The average time taken for half a given number of nuclei of a particular radioisotope to decay is the half-life of that radioisotope; values range from a fraction of a second to thousands of millions of years. See also radiometric dating.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

radioactive decay

[¦rād·ē·ō′ak·tiv di′kā]
(nuclear physics)
The spontaneous transformation of a nuclide into one or more different nuclides, accompanied by either the emission of particles from the nucleus, nuclear capture or ejection of orbital electrons, or fission. Also known as decay; nuclear spontaneous reaction; radioactive disintegration; radioactive transformation; radioactivity.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Note that in our model irreversibility is a consequence of the radioactive decay of the quantum vacuum.
A non-parametric Runs test is implemented here to verify the randomness in the radioactive decay of the given source [9-10].
If the fertile mantle has average heat production rate are 0.1 mW/m3, the mantle heat flow by radioactive decay in the 120 - 150 km thick mantle varies from 12 mWm-2 to 15 mWm-2.
Although, conclusions could not be definitely established regarding a diurnal variation of the radioactive decay, a clear peak was observed in the 12:004:00 PM time interval on 26 August 2001, far exceeding two-sigma in alpha particles per 4 hour interval.
He begins with basics--defining radiation, for instance, and discussing atomic structure--and proceeds to mathematics, radioactive decay, and other topics.
Certain elements within the Earth can send off geoneutrinos when undergoing a process called radioactive decay.
Since this is already in the ground where its radioactive decay products can cause problems (such as radon gas seepage), I fail to see what he means by "it's no good burying the stuff" unless he is suggesting that the disposal of nuclear waste is a matter of reburying previously dug up natural uranium.
"We haven't started waste retrieval in those parts of the estate where the degradation and radioactive decay has been at its greatest."
Inside the crystal, radioactive decay occurs and tiny atomic fragments called alpha particles shoot away from the decaying nucleus, which recoils like a rifle.
Although helium does accumulate in the atmosphere through radioactive decay of heavy elements in the Earth's crust, the levels aren't high enough to make this a viable source.
The amount of radiation received by people in close proximity to the patient is proportional to the size of the radiation dose, the length of time since the dose (radiation is decreased by rapid excretion of the isotope and its radioactive decay), and the length of time in proximity to the patient.
For example, the radioactive decay of a radioactive isotope (as far as we have thus measured) is fixed and does not depend on normal physical variables - this is why carbon dating is regarded as a valuable tool by archaeologists.